Mannans

Source: Wikipedia, the free encyclopedia.
For other uses, see Mannan.
Subunit of a typical mannan showing four 1,4-linked beta-D-mannose units, one with a galactose side chain.

Mannans are polymers containing the sugar mannose as a principal component.[1][2] They are a type of polysaccharide found in hemicellulose, a major source of biomass found in higher plants such as softwoods. These polymers also typically contain two other sugars, galactose and glucose. They are often branched (unlike cellulose).

Structural diversity

sulfate esters
side chains.

mannan-binding lectin pathway.[citation needed
]

Synthesis and degradation

Guanosine diphosphate mannose is the precursor to mannans.[3]

GDP-mannose is a substrate for glycosyltransferase for enzymes called mannosyltransferases.[4]

Biosynthesis

GDP-mannose is produced from

mannose-6-phosphate by the enzyme mannose-1-phosphate guanylyltransferase
.

The degradation of mannans (and many related forms of hemicellulose) has been well studied. The hydrolysis of the main mannan backbone is catalyzed by various enzymes including β-

mannase. The side chains are degraded by esterases and α-galactosidase.[1]

When a long chain of mannan is

hydrolyzed into shorter chains, these smaller molecules are known as mannan oligosaccharide (MOS). MOS by definition can be produced from either insoluble galactomannan or soluble glucomannan, although the latter type is more widely marketed.[5]

Glucomannan MOS is used as prebiotics in animal husbandry and nutritional supplements due to its bioactivity.[citation needed]

Etymology

From 'manna', produced by several species of tree and shrub e.g. Fraxinus ornus from whose secretions mannitol was originally isolated.

See also

References

  1. ^
    S2CID 9746196
    .
  2. ^ Mannan at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
  3. PMID 14670712
    .
  4. S2CID 17501948
    .
  5. PMID 31304065
    . MOS is often prepared by hydrolysis reaction of a mannose-contained glucan polymer, mainly glucomannan and galactomannan.

Further reading
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